The sera Prefix Filter is a media reactor. It allows enhancing the filter volume of a connected filter by up to 0.4 gal (1.6 l) with two variably useable filter baskets. The motor less filter is, for instance suitable as a prefilter in case of cloudiness, as a quick filter in case of pollution or as a bio filter for expanding the filter capacity of small external filters. The filter can be connected to a pump or an external filter by means of a hose. Connecting several Prefix filter in series is also possible.